The present invention relates to a hydrophobic sorbent material, particularly for the sorbing of oil from the surface of water, and to a method for its manufacture.
Unquestionably, a serious problem which long has plagued industrial and environmental concerns is the removal of oil from unwanted areas into or onto which it has been discharged. Of particular concern, of course, is the removal of unintentionally discharged oil from water or shore areas as occurs as a result, for example, of oil tanker accidents at sea or mishaps in the loading or unloading of oil from these tankers in port. Other occasions where oil removal is of concern run the gamut from relatively major problems such as the discharge of oil at areas around oil wells and oil storage facilities or the cleaning of surfaces in which oil was stored (e.g., on-shore storage tanks, oil holds of tankers) to more mundane problems such as the unintentional discharge or leaking of oil from vehicles onto road or driveway surfaces.
It is not surprising, therefore, that numerous solutions have been proposed for dealing with the problem of removing oil from unwanted areas. One class of proposed remedies relies upon bacterial degradation of oil, but such methods are extremely expensive, raise enumerable enviromental concerns and are not particularly effective in many areas and under many conditions typically encountered, for example, the low temperatures of sea water into which oil has been spilled.
Another class of proposed remedies falls broadly under the category of oil sorbents or absorbents, which are intended to remove oil from an undesired surface or areas through physical or quasi-chemical sorption forces, i.e., wherein the oil per se is not chemically broken down, decomposed or otherwise altered. Sorbent materials proposed for use in oil removal embrace a wide variety of products, ranging from sand to complex, chemically treated cellulosic materials. In general, none of the proposed sorbents is particularly well suited for the sorption of heavy oils associated with the most troublesome and serious accidental oil discharges. Indeed, this fact is so widely accepted that tests of the sorption ability of proposed products uniformly empoly number one heating oil, which is a very light oil fraction differing substantially, in its ability to be sorbed, from the heavy oils, e.g., crude oil.
Apart from this and other general deficiencies, each particular sorbent or class of sorbents presents added difficulties. For example, the inability of many sorbents to resist sorption of water is a very serious limitation considering that the most serious oil clean-up operations involve discharge of oil in seas or other bodies of water. Attempts have been made in the past to impart the requisite hydrophobicity to oil sorbents but, even where some success was obtained, the cost involved often is prohibitive.
A particularly serious limitation of many sorbents, moreover, is the fact that, once the oil has been sorbed, the sorbent/oil complex still exhibits the stickiness of the oil, presenting as many difficulties in disposing of the oil-laden sorbent as existed in removing the oil from the undesired area or surface. in addition it is found that many oil sorbents do not retain sorbed oil for a period of time sufficient to accomplish removal of the sorbent/oil complex from the site of the oil discharge before the sorbent "gives up" the oil to the same or some other undesired site.
Examples of sorbents of the type described abound in the literature. For example, in U.S. Pat. No. 3,630,891 there is disclosed an oil sorbent prepared from wood fibers which have been treated with sizing material to render the fibers water repellant. A similar product is described in U.S. Pat. No. 3,770,575 wherein wet wood pulp is treated with sizing and subjected to flash drying. U.S. Pat. No. 3,382,170 describes an oil absorbent comprised of expanded perlite, a mineral containing a substantial quantity of silica. Other silica or silicate-based oil absorbents are described in German Patent Nos. 1,248,197 and 1,519,797. U.S. Pat. No. 3,591,524 describes an oil absorbent comprised of a cellulosic base impregnated with a complex oil-in-water, ammonium or amine-containing emulsion. In U.S. Pat. No. 3,756,948, polystyrene foam crumbs are used for oil absorbtion.